Dependence of the Io-related decametric radio emission of Jupiter on the central meridian longitude and Io's “active” longitudes

Context.The statistical analysis of the Io-related decametric radio emission of Jupiter shows that this emission depends precisely on the central meridian longitude. This dependence is the result of the existence of Io's “active” longitudes, i.e. particular regions of Io's orbit, which are fixed with respect to the Jovian magnetic field and at which Io-related emission occurs more often. Aims.The paper considers the mechanism of the formation of Io's “active” longitudes. Methods.The formation of Io's “active” longitudes is caused by two factors: first, the change of the efficiency of particle acceleration in Io's ionosphere, depending on Io's longitude, and second, the degree of broadening of the angular spectrum of accelerated electrons during their passing through the plasma torus. Results.It is shown that the mechanism considered explains rather well why Io-related decametric bursts begin to appear much more often in longitudes of the range $120\degr \la \lambda_\mathrm{Io} \la 300\degr$ ($\lambda_\mathrm{Io}$ is the longitude in the frame III), and why one predominantly observes the emission from the sources located in the northern Jovian hemisphere